HIF1A and breast cancer: Similarly, our results showed that Rac1 Q61L increased HIF-1α protein expression in MCF-7 cells while preventing Rac1 activity by Rac1 T17N and siRNA Rac1 increased the HIF-1α protein and VEGF mRNA reduction under hypoxia, suggesting that hypoxia-induced Rac1 activity was responsible for the expression and activation of HIF-1α in breast cancer cells.